Power plant



May 5, 1931.

w. H. ARMACOST POWER PLANT Filed July 22, 1927 h l /btllf Armacos/ A TTORNEY.

IN VEN TOR.

Patented May 5, 1931 UNITED STATES PATENT OFFICE WILBUB n. ammoosr, on NEW Yon, n. Y., assrenon 'ro THE surnannarnn oomrm, on NEW roux, N. Y.

POWER PLANT Application filed July 22,

My invention relates to steam power plants, and has particular reference to'that type of plant wherein steam is generated at at least two different pressures, and the steam generater at the highest pressure utilized in one or more low ressure stages after having been exhausted rom a high pressure prime mover.

' In order to increase the capacity and efficiency of numbers of existing power plants as Well as to provide the most eflicient form of new plant, it is becoming increasingly common to install power generating units operating at extremely high pressures and exhausting steam at pressures high enough so that it may be utilized in power generating units operating at what has heretofore been considered normal pressures.

Such high pressure apparatus can, however, be efiiciently operated only. under comparatively constant loads, as any marked variation in the load on such units'produces not only losses in thermal efficiency, but operating difliculties which make such operations practically impossible.

In power plants where a constant base load is carried, the installation of high pressure units exhausting to low pressure units is a comparatively simple matter, but in cases where the plant operates to supply a fluctuating load, it must be designed to permit a degree of flexibility in operation which has heretofore precluded in many cases the use of high pressure units because of their characteristic requirement ofsubstantially con stant load operation.

The present invention has for its primary object the reconciliation of these conflicting conditions by the provision of a novel method of operation and suitable apparatus for carrying the method into effect.

The more detailed objects of the invention, and the advantages to be derived from its use will appear more clearly from the following description of two illustrative examples of plant layouts shown in the accompanying drawings, in which Fig. 1 is a diagrammatic elevation, partly in section of oneform of plant layout, and Fig. 2 is a similar view of another form of design.

Referring now to Fig. 1, the numeral 1 in- 1927. Serial No. 907,703.

dicates a steam generating unit, including a superheater 2, designed to generate and superheat steam at relatively high pressure.

A high pressure prime mover 3 receives steam from the superheater 2 through the valved conduit 4. At 5 is indicated a main low steam supply line which receives steam from the low pressure steam generatin units, one of which is shown at 6, pre erably provided'with superheater 7. The low pressure supply line supplies steam to one or more low pressure prime movers 8 and through the valved exhaust line 9. The exhaust from the high pressure prime mover is carried to the low pressure supply so that it may pass directly to the low pressure prime mover 8 together with the low pressure steam supplied through boiler 6, or .may be used to supply steam to any other units receiving their steam supply through the line 5.

A conduit 10 provided with a shutoff valve 11 and a pressure reducing valve 12 connects the high pressure steam supply line with a desuperheater indicated generally at 13, the latter discharging to the low pressure steam line of the plant through a suitable conduit provided with valve 14:.

The specific design of the desuperheater employed is not germane to the present invention, but for illustrative purposes I have so shown a type of desuperheater which is described and claimed in the pending application of R. M. Swartz et al., Serial Number 207,712, filed July 22, 1927. In this form of desuperheater the steam, after having its pressure reduced by passing through valve 12, flows through a number of U-shaped tubes 15, enclosed in a suitable casing and partially submerged b hot water supplied through the conduit 16 fi om the steam and water drum of the high pressure boiler. The steam passing through the tubes 15 is desuperheated by the transfer of heat to the water surrounding tubes 15, and the degree of desuperheating obtained is governed by the degree to which tubes 15 are submerged. The trans fer of heat to the water surroundin tubes 15 results in the evaporation of a port1on thereof, and the steam thus formed is carried through the conduit 17 to the chamber supplying the inlet end of tubes 15 so that no heat loss is incurred by the desuperheating process. The level of the water surrounding tubes 15 is controlled by means of a thermostatic valve 18, the control element of which is located in the discharge conduit leading from the desuperheater, and in addition thereto an emergency stop valve 19 is provided in the supply conduit 16, the latter valve being controlled by a float mechanism 20.

With the above, the method of operation of a plant under varying loads is as follows: When operating under a heavy plant load, sufiicient to require the operation of all power generating units in the plant, the high pressure boiler unit is operated at full capacitv, the steam generated therein being supplied to the high pressure prime mover 3 which exhausts into the low pressure steam line, the latter supplying the low pressure unit or units which also receive steam from the low pressure boiler 6. Under these conditions, the valves 11 and 14 are closed, and the desuperheater is not operated. In this form of design the high pressure prime mover 3 must obviously be so designed that the exhaust therefrom will be substantially at the same temperature and pressure as the steam delivered from the low pressure boilers 6.

. If now the plant load drops, it is obvious that some portion of the generating equipment must be run at reduced rating or cut out of service, and in accordance with my invention the high pressure prime mover 3 is shut down entirely, and the high pressure boiler is maintained in operation under its normal load, the steam therefrom being delivered through the conduit 10 and the desuperheater 13 to the low pressure steam supply lines, the desuperheater being so designed that it delivers steam to the low pressure supply lines at substantially the same temperature and pressure as the exhaust steam from the prime mover 3. The low pressure power units carrying the diminished load are thereby operated directly from steam generated in the high pressure boiler, and in order to reduce the steam supply to the amount required by the low pressure power units, as many of the low pressure boilers 6 as are required are cut out of service or operated at reduced rating.

This method of operation during low plant loads does not obtain any of the thermal advantages due to the generation of steam at high pressure, but it enables the high pressure boiler to be operated under uniform load conditions, a requisite to the successful operation of such boilers, and thereby enables the increased efiiciencies due to high pressure steam generation to be obtained during all such periods when the plant load is sufficient to call for the operation of both high and low pressure. prime movers.

In Fig. 2, I have shown a plant designwhich is in general similar to that illustrated in Fig. 1, but in which a reheater is included between the high pressure prime mover and the low pressure steam supply. In the form shown in Fig. 2 the plant comprises a high pressure boiler 1' and superheater 2 delivering steam to thehigh pressure prime mover 3 through the valved conduit 4. The low pressure steam supply main 5' is supplied by low pressure boilers 6 and superheaters 7, and furnishes steam to one or more low pressure prime movers 8. The valved exhaust line 9 from the high pressure prime mover 3 leads to the low pressure steam supply line 5 and has interposed therein a reheater which I have shown in the form of a radiant type heater comprising a plurality of tubes 21 disposed in the combustion chamber of the high pressure boiler 1. It is to be understood, however, that this form of reheater is illustrative only, and that other forms of reheaters may be used with equal facility, either in the high pressure'boiler or in other locations.

A high pressure steam supply conduit 10 provided with valve 11' supplies through a reducing valve 12' a desuperheater 13' similar to the one shown in Fig. l, and the steam passing from the desuperheater is carried by the conduit 22 to a point in the exhaust steam line 9 between the valve therein and the reheater 21. The flow of steam through conduit 22 is controlled by a valve 14.

The operation of the plant just described is generally similar to the operation of a plant such as is shown in Fig. 1 the principal difi'erence in the two plants eing that in the form shown in Fig. 2 the high pressure prime mover 3 abstracts enough heat from the high pressure steam so that additional heat must be imparted thereto before it can be delivered to the low pressure mains. lVhen the high pressure prime mover is operating under heavy plant load conditions, the reheater 21 is cooled by the passage of the steam therethrough, but upon the shutting down of the high pressure prime mover the reheater would soon become overheated and damaged if steam were not supplied thereto while the boiler 1 continued in operation. Steam from the high pressure boiler is, therefore, desuperheated in the desuperheater 13 so that the steam discharged therefrom will be at substantially the same pressure and temperature as the normal exhaust from the prime mover 3', and this steam is passed through the reheater and additional heat added thereto before it is delivered to the low pressure steam supply lines, in the same manner that the exhaust steam from the prime mover is treated. By thus desuperheating and reheating the steam, it is possible to pass steam through the reheater regardless of plant load conditions or of the manner in which the prime movers are handled in the operation of the plant.

Many variations in the form and arrangement of the apparatus shown will be apparent to those skilled in the art, but the invention is not to be considered as limited by the illustrative embodiments shown, and is to be considered as embracing all that may fall within the scope of the appended claims.

I claim:

1. In a power plant, a high pressure steam generator and superheater, a high pressure prime mover receiving steam from said superheater, asouree of low pressure steam delivering to a low pressure steam supply line, a connection delivering exhaust steam from said prime mover to said low pressure steam supply line, a conduit connecting said high pressure generator with said low pressure steam supply line, a desuperheater located in said connection, and means for isolating either said prime mover or said desuperheater from both said steam generator and said low pressure steam supply line.

2. In a power plant, a high pressure generator and superheater, a high pressure prime mover, a source of low pressure steam delivering to a low pressure steam supply line, a valved conduit connecting said generator with said prime mover, a valved exhaust line connecting said prime mover with said low pressure steam supply line, a desuperheaterhaving an inlet and an outlet, a valved conduit connecting said superheater with the inlet of said desuperheaten'a valved conduit connecting the outlet of said desuperheater with said low pressure steam supply line, and a pressure reducing valve located in the conduit leading to said desuperheater.

3. In a power plant, a high pressure steam generator and superheater, a high pressure prime mover, a source of low pressure steam delivering to a low pressure steam supply line, a valved conduit connecting said steam generator with said prime mover, a valved exhaustline leading from said prime mover to said low pressure steam supply line, a reheater located in said exhaust line, and means for supplying steam to said reheater when saig high pressure prime mover is not operate 4. In a power plant, a high pressure steam generator and superheater, a high pressure prime mover, a source of low pressure steam delivering to a low pressure steam supply line, a valved conduit connecting said steam generator with said prime mover, a valved exhaust line leading from said prime mover to said low pressure steam supply line, a reheater located in said exhaust line, a desuperheater having an inlet and an outlet, a valved conduit leading from said steam generator to the inlet of said desuperheater, and

a valved conduit leading from the outlet of said desuperheater to a point in said exhaust line between said prime mover and said reheater.

5. In a power plant, a high pressure steam generator and superheater, a high pressure prime mover, a source of low pressure steam delivering to a low pressure steam supply line, a valved conduit connecting said generator with said prime mover, an exhaust line leading from said prime mover to said low pressure steam supply line, a reheater located in said steam generator, and means for supplying steam from said generator to said reheater when said prime mover is not operated.

6. In a power plant, a high pressure steam generator and superheater, a high pressure prime mover, a source of low pressure steam delivering to a low pressure steam supply line, a valved conduit connecting said generator with said primemover, a valve exhaust line leading from said prime mover .to said low pressure steam supply line, a

reheater located in the furnace of said steam generator and exposed to the radiant heat therefrom, and means for supply steam to said reheater when said prime mover is not operated.

. WILBUR H. ARMACOST. 

